The thing I like about the new CG grates is that they're quite inexpensive and they're also reversible. The bars on one side are thicker than the other side, so you get a choice of two types of grill marks. I use the thinner side for chicken and other smaller pieces of meat, while the thicker side gives really fat grill marks on steaks of all kinds, like this fine example below:
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I really like that 22.5 inch round CI grate. I'll get one of those when I'm ready to replace the wire grate on my Weber.

The CG grates look nice too. Four of them would make an inexpensive replacement for the chipped and worn porcelain-coated CI grates on my Barbecues Galore Turbo Quad gas grill, except that at 19.75" x 6.75", they are a little too long and not quite wide enough.

Four of them would be 27 inches wide, which is 3.5 inches short of my grill width. Five of them would be 3.25 inches too wide. The length of 19.75 is .625 inches too long.

How hard is it to grind cast iron? Can it be done with a hand grinder? How about cutting cast iron with a cutoff wheel?

yeh, but as the second or third choice of options it would work. I replaced the porcelain grates with CI -- they look great.

They also tend to last longer if you treat 'em right, too. I don't like porcelain grates at all because they can sometimes lose small chunks of the porcelain coating and it winds up in your meat - and then in your teeth. This is especially true if you use a stainless steel brush and not a brass brush.

Unlike propane, you'll never wake up scorched and naked in another county because you mishandled a bag of briquettes.

Not the same product at all. In fact, I'd venture to guess it's yet another cheap knockoff.

Aluminum doesn't work nearly as well as cast iron anyway, so the Mangrate and Larry Wolfe grates are in a whole different class of product. This I know from experience - I've wrecked a few cooks using aluminum pans and utensils. I think a lot of the reason behind this is that it just doesn't conduct heat well or season the way cast iron does. It also has an annoying tendency to scratch, and the fact that these aluminum grates are "aircraft grade" makes precisely no difference whatsoever.

At least I'm polite about it, though. A friend of mine who is an executive chef at the local Westin hotel said it more bluntly once when a new apprentice showed up with an aluminum pan in his toolkit. He said something like "keep that cheap ---- out of my kitchen."

I'm with him.

Unlike propane, you'll never wake up scorched and naked in another county because you mishandled a bag of briquettes.